The processing of blood has been performed to remove a variety of blood constituents for therapeutic purposes. Examples of blood processing methods include hemodialysis that allows to remove metabolic waste products from the blood of patients suffering from inadequate kidney function. Blood flowing from the patient is filtrated to remove these waste products, and then returned to the patient. The method of plasmapheresis also processes blood using tangential flow membrane separation, to treat a wide variety of disease states. Membrane pore sizes can be selected to remove the unwanted plasma constituents. Blood can be also processed using various devices utilizing biochemical reactions to modify biological constituents that are present in blood. For instance, blood components such as bilirubin or phenols can be gluconized or sulfated by the in vitro circulation of blood plasma across enzymes that are bonded to membrane surfaces.
Various techniques, such as centrifugation, have been available for washing blood cells prior to returning them to the patient. In such techniques a centrifuge is used for separating and washing the red cells in batches. This is a relatively slow process, the apparatus for performing which can be complex and expensive.
Presently used technologies are generally deficient with respect to supporting patients with compromised liver function, for example. Conventional systems and methods suffer from various problems associated with sustaining such patients until a suitable donor organ can be found for transplantation or until the patient's native liver can regenerate to a healthy state.